Excess iron-induced changes in the photosynthetic characteristics of sweet potato |
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| Authors: | Adamski Janete M Peters José A Danieloski Rodrigo Bacarin Marcos A |
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| Affiliation: | a Laboratório de Cultura de Células e Tecidos Vegetais, UFPel, Instituto de Biologia, Depto. Botânica, Campus Universitário S/N., CEP 96160-000, Capão do Leão, RS, Brazil
b Laboratório de Metabolismo Vegetal, UFPel, Instituto de Biologia, Depto. Botânica, Campus Universitário S/N., CEP 96160-000 Capão do Leão, RS, Brazil
c Bolsista de Iniciação Científica, UFPel, FAEM, Campus Universitário, S/N., CEP 96160-000, Capão do Leão, RS, Brazil |
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| Abstract: | Iron (Fe) is an essential nutrient for plant growth and development. In plant tissues, approximately 80% of Fe is found in photosynthetic cells. This study was carried out to determine the effect of different iron concentrations on the photosynthetic characteristics of sweet potato plants. The fluorescence transient of chlorophyll a (OJIP), chlorophyll index and gas exchange were measured in plants grown for seven days in Hoagland solution containing an iron concentration of 0.45, 0.90, 4.50 or 9.00 mM Fe (as Fe-EDTA). The initial and maximum fluorescence increased in the plants receiving 9.00 mM Fe. In the analysis of the fluorescence kinetic difference, L- and K-bands appeared in all of the treatments, but the amplitude was higher in plants receiving 4.50 or 9.00 mM Fe. In plants grown in 9.00 mM Fe, the parameters of the JIP-Test indicated a better efficiency in the capture, absorption and use of light energy, and although the chlorophyll index was higher, the net photosynthesis was lower. The overall data showed that sweet potato plants subjected to high iron concentrations may not exhibit the toxicity symptoms, but the light reactions of photosynthesis can be affect, which may result in a declining net assimilation rate. |
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| Keywords: | ABS/RC, absorption flux (of antenna chlorophyll) per RC or a measure of PSII apparent antenna size ABS/CS0, absorption flux per CS CS, excited cross section ET0/CS0, electron transport flux per CS ET0/RC, electron transport flux (further than QA&minus ) per RC F0 = F50 μs, minimum fluorescence, when all PSII RCs are open F2(100 μs) and F3(300 μs), fluorescence intensity at 100 and 300 μs, respectively F4(2 ms) and F5(30 ms), fluorescence intensity at the J-step (2 ms) and the I-step (30 ms), respectively FM, maximum fluorescence, when all PSII RCs are closed N, turnover number as reduction, oxidation, re-reduction of QA in the timespan from light on until reaching FM OEC, oxygen-evolving complex PIABS, performance index (potential) for energy conservation from photons absorbed by PSII to the reduction of intersystem electron acceptors PItotal, performance index (potential) for energy conservation from photons absorbed by PSII to the reduction of PSI end acceptors PQH2, plastoquinol PSI, photosystem I PSII, photosystem II QA, primary quinone acceptor of PSII RC, reaction centre RC/CS0, the number of active PSII RCs per cross section RE0/CS0, electron flux-reducing end electron acceptors at the PSI acceptor side per CS RE0/RC, electron flux-reducing end electron acceptors at the PSI acceptor side per RC ROS, reactive oxygen species Sm = EC/RC, total electron carriers from water to NADPH per reaction centre of PSII TR0/CS0, trapped energy flux per CS TR0/RC, trapped energy flux (leading to QA reduction) per RC VOP, variable fluorescence between steps O (50 μs) and P VOK, variable fluorescence between steps O (50 μs) and K (300 μs) VOJ, variable fluorescence between steps O (50 μs) and J (2 ms) VOI, variable fluorescence between steps O (50 μs) and I (30 ms) VIP, variable fluorescence between steps I (30 ms) and P φP0 = TR0/ABS, maximum quantum yield of primary photochemistry φE0 = ET0/ABS, quantum yield for electron transport φR0 = RE0/ABS, quantum yield for the reduction of end acceptors at the PSI acceptor side ψE0=ET0/TR0, efficiency/probability that an electron moves further than QA&minus δR0 = RE0/ET0, efficiency/probability with which an electron from the intersystem electron carriers is transferred to reduce end electron acceptors at the PSI acceptor side |
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